MAC architecture in wireless communication systems supporting H-ARQ

ABSTRACT

A medium access control (MAC) architecture determines transmission latency and block error rate requirements for a plurality of data flows, each data flow having an associated priority and each data flow comprising a plurality of data blocks. The MAC architecture specifies a scheduling entity that determines when transmissions are serviced, and by which hybrid automatic repeat request (H-ARQ) entity. H-ARQ entities determine whether each prior block had been successfully transmitted and, if not, request retransmission of unsuccessfully transmitted data blocks. The scheduling of the data blocks takes into account whether or not the previously transmitted data blocks require retransmission. The MAC architecture allows the scheduling entity the ability to initiate new transmissions at any time and to reinitiate previously unsuccessful transmissions at any time.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The application claims priority from Provisional PatentApplication No. 60/343,661, filed Oct. 19, 2001.

BACKGROUND

[0002] The present invention is related to MAC architecture in awireless communication system where Hybrid Automatic Repeat Request(H-ARQ) techniques are applied.

[0003] A block diagram of the UMTS Terrestrial Radio Access Network(UTRAN) MAC-hs layer architecture is illustrated in FIG. 1, and a blockdiagram of the user equipment (UE) MAC hs architecture is shown in FIG.2. The UTRAN MAC-hs 30 shown in FIG. 1 comprises a Transport FormatCombination (TFC) selection entity 31, a scheduling device 32, aplurality of H-ARQ processors 33 a, 33 b and a flow controller 34.

[0004] The UE MAC-hs 40 comprises an H-ARQ processor 41. As will beexplained in further detail herinafter, with reference to both FIGS. 1and 2, the H-ARQ processors 33 a, 33 b in the UTRAN MAC-hs 30 and theH-ARQ processor 41 in the UE MAC-hs 40 work together to process blocksof data.

[0005] The H-ARQ processors 33 a, 33 b in the UTRAN MAC-hs 30 handle allof the tasks that are required for H-ARQ to generate transmissions andretransmissions for any transmission that is in error. The H-ARQprocessor 41 in the UE MAC-hs 40 is responsible for generatingacknowledgements (ACKs) to indicate a successful transmission andnegative acknowledgements (NACKs) in the case of failed transmissions.The H-ARQ processors 33 a, 33 b and 41 process sequential data streamsfor each user data flow. Blocks of data received on each user data floware sequentially assigned to H-ARQ processors 33 a, 33 b. Each H-ARQprocessor 33 a, 33 b initiates a transmission, and in the case of anerror, the H-ARQ processor 41 requests a retransmission. On subsequenttransmissions, the modulation and coding rate may be changed in order toensure a successful transmission. The H-ARQ processor 41 in the UEMAC-hs 40 may combine the soft information from the originaltransmission and any subsequent retransmissions. The data to beretransmitted and any new transmissions to the UE are forwarded to thescheduling device 32.

[0006] The scheduling device 32, coupled between the H-ARQ processors 33a, 33 b and the TFC selector 31, functions as radio resource manager anddetermines transmission latency in order to support the required QoS.Based on the outputs of the H-ARQ processors 33 a, 33 b and the priorityof new data being transmitted, the scheduling device 32 forwards thedata to the TFC selection entity 31.

[0007] The TFC selection entity 31, coupled to the scheduling device 32,receives the data to be transmitted and selects an appropriate dynamictransport format for the data to be transmitted. With respect to H-ARQtransmissions and retransmissions, the TFC selection entity 31determines modulation and coding.

[0008] Data streams are processed sequentially, and each data block isprocessed until successful transmission is achieved or the transmissionfails and the data is discarded. Retransmissions signaled by the H-ARQprocess take precedence over any new data to be transmitted. Each H-ARQprocessor 33 a, 33 b performs transmissions and retransmissions untilthe data block transmission is determined successful or failed. Usingthis scheme, higher priority data transmissions may be delayed whilelower priority data retransmissions are processed until success orfailure is determined.

[0009] UE connections require support of several independent trafficcontrol signaling channels. Each of these channels has QoS requirements,which include guaranteed and/or acceptable transmission latency levels.Since the H-ARQ processing is taken into account prior to scheduling, itis not possible for higher priority data to supercede lower prioritydata retransmissions. Therefore, the transmission latency QoSrequirements for high priority data transmissions may not be achievablewhen low priority data transmissions have been previously assigned toH-ARQ processors 33 a, 33 b.

[0010] Since retransmissions are combined with previous transmissions inthe H-ARQ process, it is possible that if the first transmissions aresufficiently corrupted, subsequent retransmissions will not achievesuccessful transmission. In this case since transmissions can not bereinitiated as new transmissions from the scheduling entity 32, data isdiscarded.

[0011] Accordingly, there exists a need for an improved MAC-hsarchitecture both in the UTRAN and UE that allows for higher prioritytransmissions to supercede lower priority transmissions and for theability to reinitiate transmissions at any time.

SUMMARY

[0012] A medium access control (MAC) architecture that determinestransmission latency and block error rate requirements for a pluralityof data flows, each data flow having an associated priority and eachdata flow comprising a plurality of data blocks. The MAC architecturespecifies a scheduling entity that determines when transmissions areserviced, and by which hybrid automatic repeat request (H-ARQ) entity.H-ARQ entities determine whether each prior block had been successfullytransmitted and, if not, request retransmission of unsuccessfullytransmitted data blocks. The scheduling of the data blocks takes intoaccount whether or not the previously transmitted data blocks requireretransmission. The MAC architecture allows the scheduling entity theability to initiate new transmissions at any time and to reinitiatepreviously unsuccessful transmissions at any time.

BRIEF DESCRIPTION OF THE DRAWING(S)

[0013]FIG. 1 is a prior art UTRAN MAC-hs.

[0014]FIG. 2 is a prior art UE MAC-hs.

[0015]FIG. 3 is a block diagram of a UTRAN MAC-hs in accordance with thepreferred embodiment of the present invention.

[0016]FIG. 4 is a block diagram of a UE MAC-hs in accordance with thepreferred embodiment of the present invention.

[0017]FIG. 5 is a flow diagram of a procedure for permitting higherpriority transmissions to interrupt lower priority transmissions toachieve transmission seven zero latency requirements.

[0018]FIG. 6 is a flow diagram of a procedure to re-initiate failedtransmissions to achieve Block Error Rate requirements.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0019] The preferred embodiments will be described with reference to thedrawing figures where like numerals represent like elements throughout.

[0020]FIG. 3 is a block diagram of the UTRAN MAC-hs 50, preferablylocated at the Node B, in accordance with the preferred embodiment ofthe present invention. The UTRAN MAC-hs 50 comprises a TFC selector 51,a plurality of H-ARQ entities 52 a, 52 b, a scheduling andprioritization entity 53, a priority class and TSN setting entity 54 anda flow controller 55. As will be explained in detail, the components ofthe UTRAN MAC-hs 50 are coupled together in a novel manner, whichfacilitates proper scheduling prioritization for greater ability toachieve transmission latency requirements and the ability to reinitiatetransmissions at any time to reduce transmission errors within the UTRANMAC-hs 50 (shown in FIG. 3) and UE MAC-hs 60 (shown in FIG. 4).

[0021] Similar to the prior art flow controller 34 discussedhereinbefore, the flow controller 55 of the present invention shown inFIG. 3, and, coupled to the MAC-c/sh of the RNC (not shown) and thepriority class and TSN setting entity 54, provides a controlled dataflow between the Node B and the RNC, taking the transmissioncapabilities of the air interface into account in a dynamic manner.Although shown in FIG. 3 as separate components, the functionality ofthe scheduling and prioritization handling entity 53 (hereinafter, the“scheduling entity 53”) and the priority class and TSN setting entity 54(hereinafter, the “TSN setting entity 54”) may be combined into a singleentity.

[0022] TSN setting entity 54 is coupled between the flow controller 55and the scheduling entity 53. The TSN setting entity 54 of the presentinvention sets, for each priority class, a queue identifier and TSN foreach new data block being serviced to ensure sequence in delivery ofdata blocks to higher layers. The TSN is unique to each priority classand queue identity within a high speed downlink shared channel(HS-DSCH), and is incremented for each new data block. Once a queueidentifier and the TSN have been set for a new data block, the datablock is forwarded to the scheduling entity 53.

[0023] The scheduling entity 53 processes data received from the TSNsetting entity 54. The scheduling entity 53 functions as a radioresource manager for the cell, as well as maintaining QoS requirementsfor the users serviced by the UTRAN MAC-hs 50. The TSN and priorityclass identifiers for the data blocks to be transmitted are forwarded tothe scheduling entity 53.

[0024] In accordance with the present invention, the scheduling entity53 ensures proper prioritization of transmissions according to data flowQoS latency requirements and allows for reinitiation of failed H-ARQtransmissions that permits the greater ability to achieve QoS BlockError Rate (BLER) requirements. These abilities of the scheduling entity53 are not possible when H-ARQ processing precedes the schedulingfunction as in the prior art system of FIG. 1. The scheduling entity 53manages HS-DSCH physical resources between the H-ARQ entities 52 a, 52 band data flows according to their QoS requirements for transmissionlatency and transport channel BLER requirements. Beside the QoSparameters, the scheduling algorithm used by the scheduling entity 53may also operate according to, for example, various radio controlresource parameters such as the signal-to-interference ratio (SIR),available and rate, speed of the UE, current load of the cell and otherfactors that are well known to those of skill in the art. The schedulingentity 53 determines the data (associated with a particular UE), and theH-ARQ entities 52 a,52 b that will service the transmission.

[0025] The transmission assigned to the H-ARQ, 52 a,52 b is either a newtransmission, or a retransmission of data that previously was notsuccessfully delivered. Status reports from the previous transmissionsignaled between the UE H-ARQ entity 61 (shown in FIG. 4) and the UTRANH-ARQ entities 52 a, 52 b (shown in FIG. 3) are relayed to thescheduling entity 53 where it is determined whether a new orretransmission will be serviced. The UTRAN MAC-hs 50 architecturedefined by the present invention allows the scheduling entity 53, at anytime, to determine whether or not to permit new transmissions to beinitiated on an H-ARQ entity 52 a, 52 b. New transmissions may be higherpriority transmissions that need to supercede lower prioritytransmissions to achieve QoS transmission latency requirements, orreinitiation of previously failed or interrupted transmissions toachieve QoS transport channel BLER requirements.

[0026] The algorithm within the scheduling entity 53 schedules datatransmissions according to priority class. The UTRAN MAC-hs 50 of thepresent invention allows lower priority transmissions to be interruptedfor the transmission of higher priority transmissions, and provides theability to reinitiate previously failed or interrupted transmissions atany time.

[0027] The scheduling entity 53 forwards radio resource schedulinginformation to the H-ARQs entities 52 a, 52 b. The scheduling entity 53directs the H-ARQ entities 52 a, 52 b to initiate either a newtransmission or a retransmission of a previous unsuccessful transmissionby the particular H-ARQ entity 52 a, 52 b. The data is then forwarded tothe TFC selector 51 for transmission. The TFC selector 51, coupled tothe H-ARQ processors 52 a, 52 b, receives the transmissions and selectsan appropriate dynamic transport format parameter for the data to betransmitted to the UE. Although shown in FIG. 3 as separate components,the functionality of the H-ARQ entities 52 a, 52 b and the TFC selector51 may be combined into a single entity.

[0028] A block diagram of a UE MAC-hs layer 60 for a UE in accordancewith the preferred embodiment of the present invention is illustrated inFIG. 4. The UE MAC-hs 60 comprises a plurality of reordering devices 62a, 62 b and an H-ARQ entity 61. Similar to the H-ARQ processor 41described hereinbefore with respect to the UTRAN, the UE H-ARQ entity 61is responsible for handling all the processes for implementing the H-ARQprotocol. Within the UE, the receiving H-ARQ entity 61 combines the softinformation from the original transmission and any subsequentretransmissions.

[0029] Within the H-ARQ protocol layer, individual transmission priorityclasses and the required sequence of delivery (TSNs) are not known.Accordingly, successful reception, transmissions are reordered accordingto their TSN by the reordering devices 62 a, 62 b. The reorderingdevices 62 a, 62 b immediately forward for processing in higher layerstransmissions following in sequence reception.

[0030] The MAC-hs process in accordance with the preferred embodiment ofthe present invention ensures that higher priority transmissions are notdelayed by processing of lower priority transmissions. Additionally,transmissions can be reinitiated at any time, thereby reducing thetransmission failure rate within the MAC-hs process. This gives thescheduling entity 53 the ability to utilize the input informationavailable to determine the best combination of transmissions to achievemaximum performance of the system, maximum use of the radio network andmaintain QoS requirements for transmission latency and BLER.

[0031] Although the elements or processes of the present invention havebeen described as discrete hardware components, for example thescheduling entity 53 and the TSN setting entity 54, these elements willmost likely be implemented in one or more software routines or modules.It should be understood that the overall flow and sequence ofinformation between each process is important, not whether the processis implemented separately or together, or in hardware or software.

[0032] Referring to FIG. 5, a method 100 for permitting transmission ofhigher priority data to interrupt the transmission of lower prioritydata to achieve transmission latency requirements is shown. The method100 is for communications between a transmitter 102 (such as at theUTRAN) and a receiver 104 (such as at the UE). The method 100 assumescommunication for a particular H-ARQ process, such as between one of theH-ARQ entities 52 a, 52 b in the UTRAN and the corresponding H-ARQentity 61 in the UE.

[0033] The method 100 commences with the setting of a new data indicator(NDI) for the establishment of a new H-ARQ process (step 103). The lowerpriority data is processed (step 106) at the transmitter 102. Asaforementioned at the receiver 104, a quality check is performed wherebyan acknowledgement (ACK) is generated if the transmission is successful(i.e. received without errors) or a non-acknowledgment (NACK) isgenerated if the transmission is not successful (step 108). The ACK orNACK is sent to the transmitter 102. Steps 106 and 108 are repeateduntil the transmission is successfully received at the receiver 104, orhigher-priority data arrives at the scheduling entity (step 110) thatneeds to be scheduled to meet QoS transmission latency requirements.

[0034] If higher priority data needs to be scheduled for transmission tomeet transmission latency requirements (step 110), lower priority datatransmission may be interrupted (step 112). The H-ARQ process oftransmission of the higher priority data is then commenced (step 114).Interruption of the previous data transmission is identified to thereceiver 104 by setting of the NDI. At the receiver 104, a quality checkis performed whereby an acknowledgement (ACK) is generated if thetransmission is successful or a non-acknowledgment (NACK) is generatedif the transmission is not successful (step 116). The ACK or NACK isthen sent to the transmitter 102. Steps 114 and 116 are repeated untilthe higher priority data transmission is successfully received at thereceiver 104.

[0035] Once the transmission of the higher priority data has beenconfirmed, the lower priority data transmission may then be reinitiated(step118). The transmission is repeated until the quality check resultsin an ACK being generated by the receiver 104 (step120). As with theaforementioned H-ARQ process, it may be necessary to retransmit thelower priority data by the transmitter 102 in response to an NACKgenerated by the receiver 104.

[0036] The method 100 of FIG. 5 is an example of scheduling of an H-ARQprocess to achieve desired latency requirements for the data to betransmitted. With the proposed UTRAN MAC architecture 50 in accordancewith the present invention, method 100 and other sequences of operationbetween the transmitter 102 and receiver 104 are also possible toachieve transmission latency requirements.

[0037] Referring to FIG. 6, a method 200 for permitting re-initiation offailed transmissions to achieve Block Error Rate (BLER) requirements isshown. The method 200 is for communications between a transmitter 201(such as at the UTRAN) and a receiver 203 (such as at the UE). Themethod 200 assumes communication for any set of H-ARQ processesassociated with a UE, such as between one of the H-ARQ entities 52 a, 52b in the UTRAN and the corresponding H-ARQ entity 61 in the UE.

[0038] The method 200 commences with the processing of data fortransmission (step 202) at the transmitter 201. The H-ARQ processing forthe data is performed, whereby a quality check is at the receiver 203 isperformed (step 204) and an ACK or NACK is then sent to the transmitter201. Steps 202 and 204 are repeated until the data transmission issuccessfully received at the receiver 203 or until a retransmissionlimit or another failure criteria is reached (step 206).

[0039] In the event that a failure criterion has been reached (step206), the UTRAN MAC architecture 50 allows for re-initiation of thefailed transmission on the H-ARQ process (steps 212 and 214).Re-initiation may be performed after the scheduling of other pendingtransmissions (steps 208, 210) or may proceed directly (steps 212, 214).Accordingly, it is possible subsequent to the transmission or failure ofone or more “other” transmissions. These other transmissions may bescheduled (step 208) and transmitted by the transmitter 201 and thequality check is performed and ACKs or NACKs are generated andtransmitted by the receiver 203 as appropriate (step 210).

[0040] Once the other transmissions have been successfully sent, or thefailure criteria has been reached (steps 208-210), the previously failedtransmission may be scheduled for transmission on the H-ARQ process(step 212). Re-initiation of the previous data transmission isidentified to the receiver 203 by setting of the NDI. Retransmissions ofthe data are sent and an ACK or a NACK is generated as appropriate (step214). Steps 212 and 214 are repeated until the transmission issuccessfully received at the receiver 203, or the retransmission limitor other failure criteria has been reached (step 206). The reinitiationof a previously failed transmission can be applied several times to anyparticular transmission in order to achieve BLER requirements.

[0041] While the present invention has been described in terms of thepreferred embodiment, other variations which are within the scope of theinvention as outlined in the claims below will be apparent to thoseskilled in the art.

What is claimed is:
 1. A method for transferring data in a wirelesscommunication system, the method comprising: receiving data blocks fortransmission and acknowledgements and negative acknowledgmentsindicating whether data blocks are required to be retransmitted;scheduling data blocks for transmission, the scheduled data blocksincluding retransmitted data blocks and the received data blocks, theprioritization based on a required transmission latency for each datablock; transmitting the scheduled data blocks based on the schedulingfrom a base station; receiving the transmitted data blocks by at leastone user equipment; and determining whether retransmission of thereceived transmitted data blocks is required and transmittingacknowledgments and negative acknowledgements in response to thedetermination.
 2. The method of claim 1 wherein the transmitting thedata blocks is over a high speed downlink shared channel.
 3. The methodof claim 1 wherein the scheduling is also based on block error raterequirements.
 4. The method of claim 1 wherein the scheduling is alsobased on a signal to interference ratio.
 5. The method of claim 1wherein the scheduling is also based on a loading of a cell of the basestation.
 6. The method of claim 1 wherein the scheduling is also basedon a speed of a user equipment receiving data blocks.
 7. The method ofclaim 1 wherein the required data latency is determined by a priorityclass of the data blocks.
 8. The method of claim 7 further comprisinginterrupting the transmission of lower priority data blocks to allow fortransmission of higher priority data blocks.
 9. The method of claim 8wherein the interrupting is indicated by transmitting a NDI.
 10. Themethod of claim 1 wherein the scheduling utilizes input information todetermine a best combination of transmissions to achieve maximumperformance.
 11. The method of claim 1 further comprising assigning eachreceived data block a transmission sequence number (TSN) prior to thescheduling.
 12. The method of claim 11 further comprising reorderingreceived transmitted data blocks based on the TSN of each receivedtransmitted data block.
 13. A radio network controller and a node-Bcomprising: a scheduling entity for receiving data blocks for schedulingdata blocks for transmission, the scheduled data blocks including thereceived data blocks and data blocks for retransmission as indicted byreceived acknowledgements and negative acknowledgements; and at leastone hybrid automatic repeat request (H-ARQ) entity for transmitting thescheduled data blocks.
 14. The radio network controller and node-B ofclaim 13 wherein the scheduling is based on a required data latency foreach data block.
 15. The radio network controller and node-B of claim 13wherein the H-ARQ entity transmits the data blocks across a high speeddownlink shared channel.
 16. The radio network controller and node-B ofclaim 13 further comprising a priority entity for assigning atransmission sequence number to each received data block prior toscheduling.
 17. The radio network controller and node-B of claim 13further comprising a flow controller for controlling the flow of databetween the radio network controller and node-B.
 18. The radio networkcontroller and node-B of claim 13 further comprising a transport formatcombination selector for selecting a transport format combination foreach transmitted data block.
 19. The radio network controller and node-Bof claim 13 wherein the scheduling entity interrupts the transmission oflower priority data blocks to allow for transmission of higher prioritydata blocks.
 20. The radio network controller and node-B of claim 13wherein the interrupting is indicated by transmitting a NDI.
 21. A radionetwork controller and a node-B comprising: scheduling means forreceiving data blocks for scheduling data blocks for transmission, thescheduled data blocks including the received data blocks and data blocksfor retransmission as indicted by received acknowledgements and negativeacknowledgements; and hybrid automatic repeat request (H-ARQ) means fortransmitting the scheduled data blocks.
 22. The radio network controllerand node-B of claim 13 wherein the scheduling is based on a requireddata latency for each data block.
 23. The radio network controller andnode-B of claim 13 wherein the H-ARQ means transmits the data blocksacross a high speed downlink shared channel.
 24. The radio networkcontroller and node-B of claim 13 further comprising priority means forassigning a transmission sequence number to each received data blockprior to scheduling.
 25. The radio network controller and node-B ofclaim 13 further comprising flow control means for controlling the flowof data between the radio network controller and node-B.
 26. The radionetwork controller and node-B of claim 13 further comprising transportformat combination selector means for selecting a transport formatcombination for each transmitted data block.
 27. The radio networkcontroller and node-B of claim 13 wherein the scheduling meansinterrupts the transmission of lower priority data blocks to allow fortransmission of higher priority data blocks.
 28. The radio networkcontroller and node-B of claim 13 wherein the interrupting is indicatedby transmitting a NDI.
 29. A user equipment comprising: a hybidautomatic repeat request (H-ARQ) entity for receiving transmitted datablocks, each data block having a transmission sequence number andtransmitted based on a sequence derived by each transmitted data block'srequired transmission latency; and at least one reordering device forreordering the received transmitted data blocks using each receivedtransmitted data block's transmission sequence number.
 30. The userequipment of claim 29 wherein the H-ARQ entity combines the soft symbolsof retransmitted ones of the received transmitted data blocks with apreviously received version of the ones received transmitted datablocks.
 31. The user equipment of claim 29 wherein the receivedtransmitted data blocks are received over a high speed downlink sharedchannel.
 32. A user equipment comprising: hybid automatic repeat request(H-ARQ) means for receiving transmitted data blocks, each data blockhaving a transmission sequence number and transmitted based on asequence derived by each transmitted data block's required transmissionlatency; and reordering means for reordering the received transmitteddata blocks using each received transmitted data block's transmissionsequence number.
 33. The user equipment of claim 32 wherein the H-ARQmeans combines the soft symbols of retransmitted ones of the receivedtransmitted data blocks with a previously received version of the onesreceived transmitted data blocks.
 34. The user equipment of claim 32wherein the received transmitted data blocks are received over a highspeed downlink shared channel.